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The Respiratory system

Pulmonary ventilation Chp 16

Respiration


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Outline

Overview of the respiratory system

Anatomy

Forces for pulmonary ventilation Factors affecting pulmonary ventilation

Clinical significance of respiratory volumes

and air flows


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Outline


Anatomy



and air flows


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Overview

Respiration = gas exchange --Occurs at the levels of thelungs and tissues (externalrespiration) and cell (internal orcellular respiration).

External respiration:

- Pulmonary ventilation:movement of air in and out

of the lungs- Gas exchange in the alveoli

- Gas transport in the blood

- Gas exchanges betweenblood and tissues


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Outline


Anatomy



and air flows


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Airways


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Airways

Upper airways:

- nose to pharynx

Lower airways:

- Conducting airway:

larynxbronchioles

- Respiratory airway:

alveoli

Due to the wall structureof the airway: one celllayer (SSE) allows forgas exchange


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Conducting airways

Presence of cartilage in the wall, fromlarynx to small bronchi preventsairway collapse.

Goblet cells secreted mucus. Ciliatedcells help move the mucus out of the

airway.

Presence of smooth muscle fibers inthe bronchioles (but no cartilage)

Volume of the conducting airway: 150ml


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Respiratory airway: Alveoli

Alveolar wall is formed by simple squamous epithelium = type I cells(SSE) gas exchange

Respiratory membrane: membrane separating alveolus from bloodcapillary.

Large surface area from the numerous alveoli better gasexchange

Presence of elastic fibers between alveoli


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Blood supply to the lungs


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Alveolar structure

Type I cells gasexchange

Type II cells secretesurfactant (lipoproteins)

decrease surfacetension allowing foreasier alveoli inflation

Surfactants start to besecreted by the 7th month

of pregnancy risk oflung disease in prematurebabies

Presence of

macrophages in alveoli


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Structure of the thoracic cavity


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The pleura

Formed by 2 layers: theparietal and visceral pleura

Roles:

- prevents friction of the lungsagainst the rib cage (due to thethin layer of liquid present inthe pleural space)

- maintains lung expansion:due to the negative pressure

within the pleural space

What is negative pressure? Whatis its importance?


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Pleura and negative pressure

Pneumothorax: lung

collapse due to air

entering in the pleural

cavity

(not to be confused

with atelectasy

alveoli collapse)


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Outline


Anatomy



and air flows


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Mechanics of breathing

Boyles law: The pressure of agas in a closed container isinversely proportional to thevolume of the container.

Air flow in the lungs is drivenby the differences in pressurebetween the atmosphere andthe alveoli

P.atm is constant changesin P.alv drive ventilation


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Inspiration and expiration

Inspiration: chest wall

expands due to musclecontraction (diaphragmand/or other muscles)

Pressure in alveoli air moves toward alveoli

Expiration: passiveprocess muscle relax chest wall return toresting state alveoli

become compressedalveolar pressure movemoves out


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Ventilation


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Outline


Anatomy



and air flows


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Factors affecting pulmonary ventilation

1- Lung compliance: ease

with which lungs can bestretched

- Compliance is ameasure of the elasticityof lung tissue and the

alveolar surface tension

2- Airway resistance: tochanges in airway radius(radiusresistance)

Pathology

lung disease resulting instiffness of tissue

no or surfactant

Asthma Airway obstruction

COPD


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Outline


Anatomy

Forces for pulmonary ventilation Forces affecting pulmonary ventilation


and air flows

L l


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Lung volumes


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Pulmonary function tests

Can help distinguish

between obstructive

pulmonary disease and

restrictive pulmonary

disease

- Obstructive disease: obstruction in

bronchi-bronchioles severely

restricts the speed and amount of

air movement

- Damage to lung tissue prevents

full lung expansion and recoil


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Anatomical dead space

Anatomical dead space:

space within theconductive airway, about

150 ml.

What will happen to aperson who has a tidal

volume of 150 ml due to

lung disease?

What can be done to help

the person?

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